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One of the biggest challenges after GBM treatment is figuring out whether a new or growing area on an MRI is real tumor growth or treatment effect such as pseudoprogression or radiation necrosis. Conventional MRI cannot reliably distinguish the two in a large portion of cases, often estimated at 30-40%.
Researchers assessed the literature to see how this problem is being addressed, including implementation of the RANO 2.0 guidelines. RANO (Response Assessment in Neuro-Oncology) is an international group that develops standardized guidelines for interpreting brain tumor scans, and its RANO 2.0 guidelines were published in 2023. Based on their review, the authors propose a tiered approach for distinguishing tumor growth from treatment effect: starting with RANO 2.0 MRI assessment, then move to advanced/perfusion MRI, then to amino-acid PET, then to biopsy when necessary. They emphasize that this is a potential framework, not yet a validated recommendation.
For patients, the practical takeaway is that when an MRI is unclear, there are increasingly more tools available to help determine what is really happening, including perfusion and amino-acid PET (and also fractional tumor burden mapping, which we've covered previously), but none can yet guarantee a definitive answer.